Water heater



Jam-23,l 1934.l w. s THoMAs 1,944,817

' WATER HEATER Filed Aug. 12, 193s` f 2 sheets-sheet 1 Juventor Xi 1 vK" attorney@ Jan. 23,

WATER HEATER 1933 2 'Sheets-Sheet 2 Filed Aug. 12

Patented Jan. 23, 1934 UNITED STATES 1,944,817 WATER HEATER William S.Thomas, Montoursvillc, Pa. Application August 12, 1933. Serial No.684,904 I s claims. (ci. 122-19) This invention relates to waterheaters, and more particularly to heaters of the storage type utilizinggas as the heating medium.

In water heatersL of this character, especially those which are intendedfor family use, it is highly important that the cost of operation berelatively low, and be maintained low over periods of long service, andthat they also be capable of a relatively quick recovery. That is, whenthe supply of hot water in the storage tank has been drawn 01T, the newsupply of relatively cold Water should be quickly and eiciently raisedto the desired temperature Withoutexcessive losses in the amount of heatgenerated by the burners.

' However, in the heaters hitherto known to the art, these `desideratahave been diflcult of concurrent attainment. Low operating cost and acapability for quick recovery have been previously considered dependentupon conflicting factors between lwhicha compromise has been necessary.For example, in order to insure rapid heating of a fresh charge ofrelatively cold Water, it has been the custom in' many of the priorheaters to increase the rate of combustion of gas to a point Where farmore heat units are produced in a given time than can be transmitted toand absorbed by the Water in the tank, with a consequent waste of heatand an increase in operating cost.

Another difficulty which has been experienced with known water heatersof tthe type to which the present invention relates is that withcontinued service there accumulates in the bottom of the tank a muddysediment or muck containing iron oxide and other impurities whichpartially insulates the bottom of the tank from the water therein andresists the rapid conduction of heat thereto from the combustion chamberbelow the tank, thereby gradually decreasing the efficiency of heatabsorption and increasing the cost of operation. So far as applicant isaware, no satisfactory means has yet been devised for preventing orminimizing this-formation of an insulating muck in the bottom of theheater tank.

Diiculty has also been encountered with'various water heaters now on themarket because of the relatively large amounts of heat which are lost inthe vented gases of combustion and by transmittal through conduction,1jradiation and convection to parts of the heat'e'structure @et incontact with the water to be heated. Coni/ction currents .in thecombustion chamber constitute a substantial source of heat losses ofthis character. Much heat is also lost in existing types of heatersbecause of the failure to provide a construction which is capable oftransmitting heat from the combustion chamber to the con tents ofthetank Aas rapidly as' that heat is generated by the burners. A I It istherefore one of the objects of the present invention to provide a waterheater o! novel construction which is not only simple in constructionand economical of manufacture but also highly efficient in operation.

Another object is to provide anew and improved water heater of thestorage type which is capable of both quick recovery and low operatingcosts over long periods of service A further object is to provide astorage water heater embodying a novelly constructed combustion chamberand tank bottom .which presents a relatively large area of highly heatconductive material betweenthe flame and the water and thus renders theheater capable of a relatively rapid transfer of heatfrom the chamberinto the water, thereby reducing the time of ame propagation necessaryfor a given temperature rise of the water in thevtank. l' I Anotherobject is to provide a new and im- 'proved tank bottom and combustion'chamber for Water heaters which notl only increases the efficiency withwhich heat is transferred Vfrom the chamber to the' contents of the tankbut also materially reduces the heat losses due to convection currentsin the Ichamber.

Still another object is to provide a storage water heater which isself-cleaning and which automatically prevents the accumulation of largeamounts of insulating sediment or muck in the bottom of the heatingtank.

A still further object is to embody in a storage water heater avtempering chamber or reservoir in which-a charge of 'relatively coldwater may be preheated by conduction from the Water in the storage tankbefore passing intoy said tank, thereby increasing the speed o1'recovery of the' heater-'that is, decreasing the time of 'flamepropagation necessary'to restore the temperature of the water inthe tankto the desired degree after some of the hotl water has been withdrawn.

Still another object is to provide a novel tempering chamber orreservoir forfa water heater which includes means for retarding orinhibiting the transfer of. heat from the preheated water within saidreservoir to the relatively cold water in the supply line leadingthereto.

A still further object is to provide a storage water heatervof novelconstruction wherein the outlet from "a preheating ortempering chamberwithin the heater tank is soconstructed and arrangedpas to direct ascouring current ol' water over thef bottom of the tank each time that acharge of 'hot wateris/withdrawn from the tank and a new supply isadmitted thereto from said chamber. f Another object isfto provideawater heater of the character described wherein the heat losses'due`tof'- convection currents in the combustion chamber are materiallyreduced by directing and substantially conning the burner ames to theinner concave portions of a plurality of domeshaped heat traps orpockets formed in the bottom of the heater tank.

A further object is to provide a novel arrangement of flow retardingbaffles for use in connection with the venting flue of a gas waterheater whereby the gases of combustion are caused to travel a tortuouspath in close contact with the walls of the heater tank and the amountof heat transferred from said gases to the contents of the tank isincreased.

These and other objects will appear more fully from a consideration ofthe detailed description of the invention which follows. Although onlyone embodiment of the invention has been de'- scribed and illustrated inthe accompanying drawings, it' will be understood that these drawingsare for purposes of illustration only and are not to be construed asdefining the scope of the invention, reference being had for thispurpose to the appended claims.

Referring now to the drawings, wherein like reference charactersindicate like parts throughout the several views:

Fig. 1 is a vertical longitudinal section,- with certain. parts brokenaway, of a gas water heater of the storage type illustrating oneembodiment of the present invention;

Fig.'2 is a horizontal sectional view taken substantially on line 2-2 ofFig. 1; and

i Fig. 3 is a plan view of the burner arrangement of the heater shown inFigs. 1 and 2.

There is shown in Fig. l of the drawings a gas l water heater of thestorage type in which are embodied those novel features of the presentinvention whereby the above mentioned objects are attained. As shown,the heater comprises a substantially cylindrical storage and heater tank4 having a suitable top 5 and a generally domeshaped bottom 6. Althoughthe tank may be constructed in any suitable manner, simplicity andeconomy of manufacture may be furthered by forming the top 5 and bottom6 as individual castings and securing them to the cylindrical wall ofthe tank in any desired manner, as by riveting or welding. While anynon.-

`corrosive, heat conductive metal is suitable for the tank, it has beenfound that when aluminum is used, particularly for the bottom casting 6,relatively high efficiency as respects heat transfer is obtained whileat the same time the cost of manufacture remains relatively inexpensive.

The tank 4 is also provided with a suitable suplply or inlet pipe 7through which relatively cold water may be fed to the interior thereof,either directly or through a vtempering reservoir or chamber 8 later tobe described. Hot water may be drawn from the tank through a suitableoutlet pipe 9. The cylindrical wall of tank 4 may extend downwardlybelow dome-shaped bottom 6 and rest upon a bottom supporting plate 10which in turn may be provided with a plurality of suitableground-engaging legs or feet 11.

The lattom 6 of tank 4, which also forms the top of the combustionchamber of the heater, is especially constructed in a new and improvedmanner not only to insure a relatively rapid transfer of heat from thecombustion chamber to the water within the tank but also to reduce to aminimum the heat losses which are occasioned by convection currents inthe combustion chamber. To this end, the main dome of bottom 6 isprovided with a plurality of spaced, auxiliary domes l2 which extendupwardly into theI tank with their upper convex surfaces well above thelevel of the muck or sediment which normally forms' in the bottom ofwater heaters of this general type. Although twelve of these auxiliarydomes have been shown in the accompanying drawings, it will beunderstood that the invention is not limited to any specific number orarrangement thereof so long as the desired objects of eiiicient heattransfer and minimization of convection losses are attained.

In connection with this feature of increased rapidity of heat transferto and absorption by the water in the tank, it will be noted that, evenln the absence of the self-cleaning and scouring feature of the presentinvention later to be described, the provision of bottom 6 with apluralityof auxiliary domes l2 insures that there will always be arelatively large surface of highly heat conductive material in directcontact with the water in the tank above the level of the normal muckline in the bottom thereof.

As is pointed out above, the bottom 6 of storage tank 4 also forms thetop of the combustion chamber of the heater, the bottom and sides ofwhich are constituted by supporting plate l0` and the lower end of thecylindrical wall of tank 4, respectively. Supporting plate 10 ispreferably perforated as shown to admit air to the combustion chamber.Within the combustion chamber there is provided suitable means forproducingthe heat which is to be transmitted, primarily through 105bottom 6, to the water within the storage tank.

In the embodiment illustrated, the heating means comprise a plurality ofinterconnected gas burners 13 each of which is mounted directly beneathone of'auxiliary domes 12 with its gas ports so 110 constructed andarranged as to direct the flame against the lower concave surface ofsaid dome.

As is shown best in Fig. l, each of domes l2 is substantiallyhemispherical and its associated burner 13 is preferably locatedsubstantially in 115 the center of the plane of the lower edge of thedome. With this construction the flame from each of burners 13 issubstantially confined to the interior of its associated dome 12 withthe result that the gases of combustion remain trapped under the dome,practically unaffected by convec= tion currents within the combustionchamber below the plane of the burner, during the transfer of arelatively large proportion of the heat units from said gases throughthe bottom 6 to 125` the water within tank 4.

The relatively high efficiency of heat transfer afforded by thisconstruction also makes possible the use of a relatively low flame ateach of burners 13. While it is true that with a low flame the number ofheat units generated per unit time is less than with a higher ame, theheat traps or pockets formed by auxiliary domes 12 and their relativelylarge conductive surfaces provide a greater opportunity for heattransfer than is given in water heaters hitherto known to the art, withthe result that the rate of combustion in the present heater can begoverned so as to generate substantially only as much heat as can beefficiently transmitted to and absorbed by the water in the tank throughthe bottom and sides thereof.

Although the specific arrangement and construction of gas burners 13,aside from their relation to domes l2, form no part of the presentinvention, it is preferable that each burner be provided with anindividual connection to a gas supply main 14 the flow of gas in whichmay be controlled in any suitable manner. These connections may, asshown, extend downwardlt7 15nthrough the air holes in supporting plate10 to a main 14 located below said plate. A pilot burner 15 is alsoprovided and is preferably located in the center of a ring 16 which isconnected to supply main 14 and provided with gas ports in its uppersurface. Pilot burner 15 may be constantly supplied with gas through aseparate connection 17 in the usual manner. Ring 16 is in turn connectedto the various main burners 13 by conduits 18 each of which is alsoprovided with suitable gas ports in the upper surface thereof. When gasis supplied to main 14, that issuing from the ports in ring 16 is rstignited by pilot burner 15 and then transmitted by means of conduits 18to the various main burners 13.

If desired, bottom 6 of the heater tank may be provided with a smalldome 19, similar to domes 12, directly above pilot burner 15 and ring16. Such a construction renders even the relatively small amount of heatproduced by the pilot ame available for maintaining the temperature ofthe water in tank 4 when the main burners are not in operation.

In order to prevent heat losses by radiation from the heater tank, andin order to extract some of the heat which remains in the gases ofcombustionat the time that they leave the combustion chamber beneath thetank, it is customary in water heaters of this general character toenclose the top and sides of the tank in a casing of suit-'- ableinsulating material, and to vent the gases of combustion to theatmosphere through .the space between the tank and the insulatingcasing. In

the form shown, tank 4 is provided with a surrounding casing 20 of anysuitable insulating material, which casing is spaced from the side wallan-d top of tank 4 and lis secured at its lower end to and supported bysupporting plate 10. Casing 20 is also provided at the top thereof Witha vent pipe 21, this vent together with the space between casing 20 andtank 4 forming a flue through which the gases of combustion are led fromthe combustion chamber to the atmosphere, the communication between thecombustion chamber and the ue being through a plurality of openings 29formed in the lower edge of the side wall of tank 4.

While theue construction thus described provides additional opportunityfor the extraction of heat from the gases of combustion before nallyexhausting them to the atmosphere, it has been found that the eiciencyof the heater can be increased if the ow of the gases through such a ueis retarded and if all of the gases can be made to come into repeated'intimate contact with the wall of the heater tank. The present inventiontherefore includes a novel arrangement of baffles which are interposedin vthe space between the walls of tank 4 and insulating casing 20 insuch a way as to cause the gases to follow a tortuous path and torepeatedly come into intimate contact with the wall of said tank.

In the form illustrated in Figs. 1 and 2, a plurality of annular baillerings 22, each of a width substantially equal to that of the spacebetween the walls of tank 4 and casing 20, and having a frictional ttherewith, are superposed one above 7 the other in said space. Eachbaffle ring 22 is provided with a port 23 of .relatively smallcircumferential amplitude formed adjacent the inner edge thereof, theports in adjacent plates being staggered in any suitable manner, as bylocating them at diametrically opposite points with respect to tank 4.uEach port 23 is preferably provided by cutting baflle ring 22 outwardlyyof tank 4. With baffle rings and ports of -this construction, the gasesleaving the combustion chamber are forced to travel in a circuitous patharound tank 4 in their passage to vent 21, and in passing through eachport 23 are forced by deflector lip 24 into intimate, wiping contactwith the wall of tank 4; The retardation in the flow of the gases thusprovided is suflicient to permit substantially complete absorption bythe water in tank 4 of all of the heat units remaining in the gases,instead of allowing this heat to be lost to the atmosphere.

As has previously been pointed out, the incoming relatively cold watermay be fed directly to the interior of tank 4 through supply pipe '7.However, it is preferable that it be first led to a tempering chamber orreservoir within the tank wherein it may be preheated by conduction bythe surrounding hot water in the storage tank. The present inventiontherefore includes a temperlng reservoir 8 of` novel construction whichnot only functions as a preheating chamber and thereby reduces the timerequired by the heater for recovery, but also is so constructed andarranged as to render the heater tank self-cleaning and capable ofautomatically preventing the accumulation of large amounts of sedimentor muck in the bottom thereof. In the form shown, tempering reservoir 8consists of a hollow, frustoconical casting secured at its upper end toand supported by the lower outwardly expanded end of supply pipe 7.Reservoir 8 is thus supported centrally Within tank -4 with its bottomclosely adjacent the upper surfaces of auxiliary domes 12.

Relatively cold water is supplied to tempering reservoir 8 through pipe7, the connection therebetween being controlled by a suitable insulatingvalve 25. It is-the purpose of valve 25 to retard or inhibit thetransfer of heat from the water Within tempering reservoir 8, which isheated by conduction from the surrounding hot water in tank 4, to therelatively cold water in inlet pipe 7, and to thereby minimize thestandby lovss which would otherwise occur if these two bodies of Waterwere in direct contact. To this end, valve 25 is so constructed as tohave a relatively low capacity for heat conduction, the valve showncomprising a body or core of a suitable insulating material, such ascork, either impregtempering reservoir 8 are full of water but to.

open under the pressure of the water in inlet pipe '7 whenever water isdrawn from reservoir 8 into tank 4` as when hot water is drawn offthrough outlet pipe 9. So long as the body of the valve is constructedof a buoyant material, such as cork, it is only necessary to pivot thevalve to the upper end of reservoir 8 as shown, or to mount it upon avertical spindle, and to permit it to seat itself against the conicalseat provided by the upper end of reservoir 8.

In order that the water which is tempered or preheated within vreservoiror chamber 8 may be supplied to tank 4 to replenish the charge thereinwhenever hot water is drawn off through outlet pipe 9, the bottom ofreservoir 8 is provided with a plurality of downwardly extending nozzles26, preferably equal in number to the number of auxiliary domes withwhich tank bottom 6 is provided, the lower end of each of said nozzlesbeing located very close to the upper surface of one of said domes. Thisarrangement of nozzles is such that, when hot water is withdrawn fromtank 4 through outlet pipe 9, the pressure of the water in inletpipe 7and reservoir 8 forces a stream of water out of each of nozzles 26, theturbulent effect of which streams impinging upon domes 12 and dome 19.is to create a scouring current of water over said domes and the bottom6x eiiectually cleaning the same and minimizing the formation ofanvinsulating deposit of sediment or muck between the water in tank 4and the heat conducting portions of the tank bottom.

atsediment'or muck may form in the bottom -of tank 4 is washed off tothe periphery of domeshaped bottom 6 where it may be drawn off at willthrough suitable drain pipes 27. If desired, one or more of drain'pipes27 may be provided with a hose coupling'28 for connection to a source ofwater under high pressure for cleaning out muck which is notreadilyremoved by ordinary draining.

In the event that it should not be desired to use a tempering reservoir8, the lower end of water supply pipe 'I may be provided with scouringnozzles similarvto those just described; or, as has been previouslypointed out, even without such means, the upper surfaces of auxiliary,domes 12 will remain highly heat conductive since they lie well abovethe normal level of any muck which may form on main dome 6.

Although it is believed that the operation of the water heater formingthe subject matter of the present invention is obvious from thepreceding description of its construction, its cycle may be summarizedas follows: Assuming that tank 4 is full of water which has been heatedto the desired degree and that 'main burners 13 are not in operation(the flow of gas in main 14 having been cut off in any suitable manner),pilot burner 15 remains burning directing its 'llame against the lowerconcave surface of dome 19, thereby continuously adding a small amountof heat to the water within the tank. At this time tempering reservoir 8and supply pipe '7 are also full of water, insulating valve 25 beingclosed due to its -property of flotation, and the water within reservoir8 gradually becomes preheated or tempered by conduction from thesurrounding hot water in tank 4. When a quantity of hot water is drawnoff from tank 4 through outlet pipe 9, valve 25 opens and the preheatedwater within tempering reservoir 8 is forcedv downwardly throughscouring nozzles 26 and causes a turbulent flow of water over and arounddomes`12 and 19 and the main dome surface of bottom 6-so as to scouraway any accumulation of muck or sediment which may have gatheredthereon and to wash it downwardly to the outer periphery of bottom 6,whence it may be removed at will through drain pipes 2'7.k

The addition to tank 4 of the relatively cool water from temperingchamber 8 reduces the temperature of the water in the tank to the pointwhere additional heat is required, whereupon the main gas supply isopened and main burners 13 become ignited from pilot 15 through ring 16and conduits 18. Due to the positioning of burners-13 at the centers of`hemispherical domes 12, the flames from said burners are directedagainst and substantially entrapped within the concave portions of saiddomes. Due to the relatively large conductive areaafiorded by domes 12,and

since these dome surfaces are free from any insulating coating of muckor sediment, the heat transfer from the entrapped products of combustionwithin domes 12 to the water in tank 4 is relatively rapid, particularlywhen the bottom of the tank is constructed of a material, such asaluminum, which possesses a high coeicient ofl heat conductivity.Moreover, since the water which is supplied to tank 4 has been temperedor preheated in reservoir 8, the time required for raising it to thede'sired temperature in tank 4 is shorter than it would be if the newcharge were added directly from inlet supply pipe '1. The recovery timeof the heater is thereby decreased. At the same time, since the gases ofcombustion are substantially entrapped beneath domes 12, the convectioncurrents through the lower part of the combustion chamber haverelatively little effect in carrying the hot gases away from the heatconductive portions of thetank bottom to be wasted in heating parts ofthe structure not in contact with the water in the tank or in passingthrough the flue to the atmosphere.

After suicient water has been supplied from reservoir 8 and pipe 7 tocompletely ll tank 4, and when reservoir 8 is again filled withrelatively cold water from pipe 7, valve 25 oats to its closedpositionand the heating continues until the water in tank 4 againreaches the desired temperature, whereupon the main burners 13 may becut 0E.

The gases of combustion which gradually pass from beneath domes 12travel through openings 29 into the iiue between tank 4 and insulatingcasing 20. The passage of these gases through the flue, however, issubstantially retarded by annular baffle rings 22 and their staggeredports 23, and they are forced into repeated intimate engagement with thewall of tank 4, so that still more heat is extracted from these gases bythe water in the tank before they pass through vent.

21 to the atmosphere.

There is thus provided by the present invention a water heater of newand improved construction which is simple in structure, highly enicientin operation and especially well adapted for installationswherefconstantly low costs of operation over periods of. long servicewithout expert supervision are essential. Due to the novel constructionof the bottom of the heater tank, which also forms the top of thecombustion chamber, a high rate of heat transmission is attainedaccompanied by a decrease in heatlosses due to convection currents inthe combustion chamber. Additional heat losses in the exhaust gases areminimized by the novel arrangement of retarding baliles which areprovided in the space between the heater tank and the surroundinginsulating casing. Quick recovery is also insured by the provision of atempering chamber or reservoir of substantial capacity wherein theincoming charge of water may be preheated before it is supplied to themain heater tank. The present heater is also characterized by theinclusion of novel means for automatically cleaning the bottom of thetank and for preventing the accumulation of sediment or muck whichnormally forms an insulating coating at the bottom of heater tanks ofthis general character and decreases the eillciency of heat transmissionand absorption.

Although but. a single example of the present inventive concept has beendisclosed, it will be obvious that the invention is not limited to theapparatus shown in the drawings, but is capable of a variety ofmechanical embodiments. For

example, any suitable heat producing means may be substituted for thespecific form of gas burners shown, which means may be controlled eithermanually of automatically in any manner known to the art. Likewise, thenumber, size and arrangement of burners and auxiliary domes may bevaried to suit the requirements of any particular installation. Also, itis obvious that the insulating valve interposed between supply pipe 7and tempering reservoir-8 may be mounted differently from the specificconstruction shown just so long as it returns to closed position whenthe tank 4 and reservoir 8 are full of water. Furthermore, it will beappreciated that certain of the features of the present invention may beused separately or in combination with any one or more of the otherfeatures without deviating from the inventive concept. Various otherchanges, which will now appear to those skilled in the art, may be madein the form, details of construction and arrangement of the partswithoutdeparting from the spirit of the invention, and reference istherefore to be had to the appended claims for a definition of thelimits of the invention.

What is claimed is:

1. In a water heater, the combination of a tank, a bottom for said tankhaving a plurality of hollow domes extending upwardly therefrom into thetank, a burner located adjacent each of said domes and so constructedand arranged as to direct a flame against the lower concave surfacethereof, the upper surface of each of said domes extending above thenormal muck line within the tank, means for supplying relatively coldwater to said tank and for directing a scouring current of water overthe upper surface of each of said domes each time that water is suppliedto said tank, and means for drawing hot water therefrom.

2. In a water heater, the combination of a tank, a dome-shaped bottomfor said tank having a plurality of spaced vauxiliary hollow domesextending upwardly therefrom into the tank, a burner located beneatheach of said auxiliary domes and so constructed and arranged as todirect a flame against the lower concave surface thereof, means forsupplying relatively'cold Water to said tank, means for drawing hotwater therefrom, and means for utilizing the pressure of said cold waterin the scouring of the upper surfaces of said auxiliary domes each timethat water is supplied to said tank.

3. In a water heater, the combination of a tank, a bottom for said tankhaving a plurality of hollow domes extending upwardly therefrom into thetank, a burner located adjacent each of said domes and so constructedand arranged as to direct a name againstthe lower concave surfacethereof, means for supplying relatively cold .water to said tank, meansfor drawing hot water therefrom, and a plurality of scouring nozzlesconnected with said supply means, each of said nozzles being soconstructed and arranged as to direct a scouring current of water overthe upper surface of one of said domes each time that water is suppliedto said tank.

4. In a water heater, the combination of a tank, a bottom for said tankhaving a plurality of spaced hollow domes extending upwardly therefrominto the tank, a burner located beneath each of said domes and soconstructed and arranged as to direct a ame against the lower concavesurface thereof, the upper surface of each of said domes extending abovethe normal muck line within the tank, means for supplying relativelycold water to said tank, means for drawing hot Water. therefrom, andmeans for directing a scouring current of water over the upper surfaceof each of said domes each time that water is supplied to said tank.

5. A water heater comprising a tank, a combustion chamber below the tankincluding an im-l perforate dome forming a closure for the bottom of thetank, said dome having cast integrally therewith a plurality of spaced,upwardly extending, hollow auxiliary domes, the upper surfaces of saidauxiliary domes extending above the normal muck line within said tank,means for supplying heat to the lower concave surface of each of saidauxiliary domes, and means for directing a scouring current of waterover the upper surface of each of said auxiliary domes each time thatwater is supplied to said tank.

6. In a water heater of the class described, a tank, a bottom for saidtank having a plurality of hollow domes projecting upwardly therefrominto said tank, means for directing a flame.

against the lower concave surface of each of said domes, means forsupplying relatively cold water to said tank, means for drawing hotwater therefrom, a tempering reservoir centrally disposed within saidtank and connected with said supply means, the Water in said temperinglreservoir being preheated by the surrounding water in said tank, and aplurality lof scouring nozzles in the bottom of said temperingreservoir, each of said nozzles being so constructed and arranged as todirect a scouring current of Water over the upper surface of one of saiddomes each time that Water is supplied from said reservoir to said tank.

7. In a Water heater of the class described, a tank, means for heatingthe water in said tank, a pipe for supplying relatively cold water tosaid tank, a. pipe for drawing hot water therefrom, a tempering chambercentrally disposed within said tank and connected with said supply pipe,and means including a valve of low heat conductivity interposed betweensaid tempering chamber and supply pipe for inhibiting the transfer ofheat from the water in said tempering chamber to the Water in saidsupply pipe.

8. In a water heater, Athe combination of a metal tank, a combustionchamber below said tank, a casing of insulating material encircling saidtank and extending over the top thereof, said casing being spaced fromthe top and sides of said tank and having an opening in the top thereofthereby forming a iiue for the escape of gases from said combustionchamber, and a plurality of annular baffle plates arranged in super-4posed relation in the space between the sides of said tank and saidcasing to retard. the flow of hot gases therethrough, each of said`baille plates having a width substantially equal to that of said spacewith a portion of relatively small circumferential amplitude extendingobliquely upwardly toward the inner edge thereof and the side of thetank to form a port, upwardly extending ,portion constituting a gasdeflector lip, the ports in adjacent plates being disposed at angularlyrelated positions with respect to the circumference of said tank,whereby the gases of combustion are caused tov travel a tortuous pathand at each port are deected into close contact with the side of saidtank, the amount of heat transferred therefrom to the contents of thetank being thereby increased.

WILLIAM S. THOMAS.

